1. Field of the Invention
The invention relates to materials crosslinkable at room temperature by condensation reaction to give permanently resilient materials, and based on organosilicon compounds in the form of multicomponent systems, processes for the preparation thereof and the use thereof.
2. Description of the Related Art
Systems crosslinkable at room temperature by condensation reaction to give resilient materials and based on organosilicon compounds having hydrolyzable groups are known. They are provided as so-called one-component systems (RTV-1) and two-component systems (RTV-2) for the processor. The difference between the two systems is in particular that one-component systems cure slowly by diffusion of atmospheric humidity from the surface into deeper layers, whereas two-component systems crosslink very rapidly even in deep layers after mixing of the two components. The readily processable one-component systems are accordingly very suitable, for example, for sealing joints in structures. Often, however, rapid curing even in deeper layers is desired, for example in the case of mold-making or casting materials. In this case, two-component systems which already contain all constituents necessary for curing are required.
Usually, all constituents of a two-component system are divided into two components so that storage-stable premixes result. Thus, for example, long-chain polymers having silanol groups and optionally water are combined in one component and organosilicon compounds having hydrolyzable groups and catalysts in a second component. Apart from these four main constituents, the materials frequently contain further ingredients, for example, fillers, plasticizers and a very wide range of additives.
Known catalysts for two-component materials crosslinking at room temperature by condensation reaction are organotin compounds. A disadvantage of these catalysts is that they are not ecologically safe. Nevertheless, they are used in relatively large amounts. Moreover, these materials have a very great tendency to reversion at relatively high temperatures, owing to the presence of large amounts of catalyst. A disadvantage of two-component systems known to date is furthermore that curing takes place with a considerable undesired shrinkage of the materials because the hydrolysis products, formed in large amounts, are released to the environment. This disadvantage is further exacerbated by the fact that the crosslinking agents have to be added in a large stoichiometric excess for reliable curing of the materials. Thus, EP-B1-595 531 describes the use of particularly large amounts of catalyst in mold-making materials. Furthermore, the use of alkoxysilanes as crosslinking agents whose alkoxy radicals have a particularly high molar mass is described therein. The existing disadvantage of the considerable shrinkage is further exacerbated by the high molar mass.